Optimization Of Groundwater Pollution Monitoring Network In Typical Polluted Areas In Pinggu Basin

With the acceleration of the process of urbanization and industrialization in our country,the environmental quality of groundwater has deteriorated and pollution problems have become increasingly prominent,which has severely affected the production and life of the people.In order to understand and grasp the spatial distribution and evolution trend of pollutants in groundwater,groundwater monitoring networks in typical polluted areas are usually set up and optimized based on the current spatial distribution of pollutants.In this paper,the contaminated area formed by the Qianruiying landfill in the Pinggu Basin is used as the research area.According to the geological and hydrogeological conditions of the contaminated area and groundwater monitoring data.First,based on the groundwater quality standard and Mann-Kendall trend test,the monitoring indicators that have a high rate of over-standard in the monitoring wells in the contaminated area and have a tendency to expand the pollution range are selected as characteristic pollutants.Through correlation analysis and principal component analysis of monitoring data,various elements related to characteristic pollutants are determined and their sources are analyzed.Afterwards,MannKendall trend analysis and spatial moment analysis were used to estimate the zero-order moment,the first-order moment and the second-order moment to determine the spatial distribution of the pollution plume and its evolution trend.Finally,the Delaunay method is used to triangulate the entire monitoring well pattern and determine the relative importance of each sampling location in the monitoring network to optimize the space.The modified CES method was used to optimize the sampling frequency of the monitoring well pattern,and an Optimize the design plan for the groundwater pollution monitoring network in the contaminated area is proposed,and the rationality of the optimized plan was evaluated.The paper got the following conclusions:(1)As the excess rate of manganese and ammonia nitrogen is the largest in the polluted area and both are in a rapid upward trend,manganese and ammonia nitrogen are taken as the characteristic pollutants in this study.Based on previous research results and source analysis,it is determined that the landfill leachate infiltrated by the Qianruiying landfill itself contains a large amount of ammonia nitrogen pollutants,and the serious pollution of manganese is due to the infiltration of landfill leachate into the vadose zone.A reducing environment is formed,and a large amount of manganese oxide is reduced.On the other hand,when the organic matter in the landfill leachate coexists with metallic manganese,the soluble manganese-organic complex is formed directly so that the manganese in the soil is dissolved and migrated into the groundwater.(2)Through Mann-Kendall trend analysis and spatial moment analysis,it is concluded that the evolution trend of ammonia nitrogen pollution plume and manganese pollution plume are both in an upward trend.Among them,ammonia nitrogen pollution sources continue to release pollutants,and the pollution range has a trend of significant expansion to the north;manganese pollution sources also Pollutants continue to be released,and the scope of pollution is expanding significantly to the south.(3)The spatial optimization results obtained by the Delaunay triangulation method show that two new monitoring wells are added to the ammonia nitrogen monitoring well pattern,and five redundant wells are removed from the manganese monitoring well pattern(PG-40,PG-42,PG-43,PG-44,PG-45).The time optimization results obtained by the revised CES method show that the sampling frequency of PG-42,PG-24 in the ammonia nitrogen monitoring network is reduced to once a year,while the sampling frequency of PG-41 is reduced to twice a year;five redundant monitoring wells in the manganese monitoring network stopped sampling,and the sampling frequency of PG-24,PG-30,and PG-32 was increased to four times a year,while the sampling frequency of PG-48 was reduced to once a year.The rationality evaluation results of the independent sample t-test method show that the monitoring network optimization plan is reasonable.